Low bend loss optical fiber with deep depressed ring

ABSTRACT

Optical waveguide fiber that is bend resistant and single moded at 1260 nm and at higher wavelengths. The optical fiber includes a core and cladding, the cladding having an annular inner region, an annular ring region, and an annular outer region. The annular ring region has a low relative refractive index.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 60/841,458 filed on Aug. 31, 2006, the contentwhich is relied upon and incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to optical fiber, andparticularly to bend resistant single moded fibers.

2. Technical Background

Optical fibers utilized in so-called “access” and fiber to the premises(FTTx) optical networks can be subjected to a variety of bendingenvironments. Optical fiber can be deployed in such networks in a mannerwhich induces bend losses in optical signals transmitted through theoptical fiber. Some applications that can impose physical demands, suchas tight bend radii, compression of optical fiber, etc., that inducebend losses include the deployment of optical fiber in optical dropcable assemblies, distribution cables with Factory Installed TerminationSystems (FITS) and slack loops, small bend radius multiports located incabinets that connect feeder and distribution cables, and jumpers inNetwork Access Points between distribution and drop cables.

SUMMARY OF THE INVENTION

Optical waveguide fiber is disclosed herein that is bend resistant andsingle moded at the wavelength of 1260 nm and at higher wavelengths. Theoptical fiber has a large effective area, which is beneficial, forexample, for inhibiting signal nonlinearities especially at high bitrates. Preferably, the optical fiber has both low macrobend inducedattenuation losses and low microbend induced attenuation losses.

The optical fiber disclosed herein comprises a glass core and a glasscladding surrounding and in contact with the core, the core beingdisposed about a centerline and extending from the centerline in aradial direction. The cladding comprises an annular inner regionsurrounding and in contact with the core region, an annular ring regionsurrounding and in contact with the annular inner region, and an annularouter region surrounding and in contact with the annular ring region andextending to an outermost glass radius. The annular outer region is theoutermost glass portion of the optical fiber. In preferred embodiments,the annular outer region is covered by one or more coatings, such as aurethane acrylate material. The annular ring region has a low relativerefractive index. In some embodiments, the optical fiber disclosedherein has a cladding with an annular ring region having relativerefractive index with a narrow and deep depression.

The maximum relative refractive index of the glass core is less than0.45%. The minimum relative refractive index of the annular ring regionis less than −0.63%, preferably less than −0.65%, more preferably lessthan or equal to −0.7%. The magnitude of the relative refractive indexof the annular inner region is low, less than 0.05%. The relativerefractive index of the majority of the radial width of the annularinner region can be positive, negative, and/or zero.

The maximum relative refractive index of the core is the greatestmaximum relative refractive index of the entire optical fiber. Themaximum relative refractive index of the annular inner region is greaterthan or equal to the minimum relative refractive index of the annularinner region. The minimum relative refractive index of the annular innerregion is greater than the minimum relative refractive index of theannular ring region.

The refractive index profiles of the optical fibers disclosed hereinprovide: a mode field diameter at 1310 nm of 8.20 to 9.50 μm, preferably8.40 to 9.20 μm; a zero dispersion wavelength of 1300 to 1324 nm; a2-meter fiber cutoff wavelength less than 1260 nm; and superior bendresistance for both macrobend and microbend. Preferably, the opticalfiber disclosed herein exhibits a 20 mm bend loss (i.e. an increase inattenuation due to macrobending when the fiber is wrapped around a 20 mmdiameter mandrel) of less than 0.05 dB/turn, more preferably less than0.03 dB/turn, at 1550 nm. Preferably, the optical fiber disclosed hereinexhibits a 10 mm bend loss (i.e. an increase in attenuation due tomacrobending when the fiber is wrapped around a 10 mm diameter mandrel)of less than 1.0 dB/turn, more preferably less than 0.75 dB/turn, at1550 nm. Preferably, the optical fiber disclosed herein exhibits a pinarray bend loss of not more than 15 dB, more preferably less than 10 dB,and even more preferably less than 5 dB. In some embodiments, thelateral load wire mesh loss is less than 0.5 dB, preferably less than0.25 dB.

In one set of embodiments, the annular ring region comprises silicaglass having a dopant selected from the group consisting of germanium,aluminum, phosphorus, titanium, boron, and fluorine.

In another set of embodiments, the annular ring region comprises silicaglass with a plurality of holes, the holes being either empty (vacuum)or gas filled, wherein the holes provide internal reflection of light,thereby providing waveguiding to light traveling along the core. Suchholes can provide an effective refractive index which is low, e.g.compared to pure silica.

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a relative refractive index profile of an embodiment of anoptical waveguide fiber as disclosed herein.

FIG. 2 shows a measured relative refractive index profile of anembodiment of an optical waveguide fiber as disclosed herein.

FIG. 3 is a schematic cross-sectional view of an embodiment of anoptical waveguide fiber as disclosed herein.

FIG. 4 is a schematic illustration of a fiber optic communication systememploying an optical fiber as disclosed herein.

FIG. 5 schematically illustrates another embodiment of an optical fibercommunication system disclosed herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Additional features and advantages of the invention will be set forth inthe detailed description which follows and will be apparent to thoseskilled in the art from the description or recognized by practicing theinvention as described in the following description together with theclaims and appended drawings.

The “refractive index profile” is the relationship between refractiveindex or relative refractive index and waveguide fiber radius.

The “relative refractive index percent” is defined as 66%=100×(n_(i)²−n_(c) ²)/2n_(i) ², where n_(i) is the maximum refractive index inregion i, unless otherwise specified, and n_(c) is the averagerefractive index of the annular outer region of the cladding. As usedherein, the relative refractive index is represented by Δ and its valuesare given in units of “%”, unless otherwise specified. In cases wherethe refractive index of a region is less than the average refractiveindex of the annular outer region, the relative index percent isnegative and is referred to as having a depressed region or depressedindex, and the minimum relative refractive index is calculated at thepoint at which the relative index is most negative unless otherwisespecified. In cases where the refractive index of a region is greaterthan the average refractive index of the cladding region, the relativeindex percent is positive and the region can be said to be raised or tohave a positive index. An “updopant” is herein considered to be a dopantwhich has a propensity to raise the refractive index relative to pureundoped SiO₂. A “downdopant” is herein considered to be a dopant whichhas a propensity to lower the refractive index relative to pure undopedSiO₂. An updopant may be present in a region of an optical fiber havinga negative relative refractive index when accompanied by one or moreother dopants which are not updopants. Likewise, one or more otherdopants which are not updopants may be present in a region of an opticalfiber having a positive relative refractive index. A downdopant may bepresent in a region of an optical fiber having a positive relativerefractive index when accompanied by one or more other dopants which arenot downdopants. Likewise, one or more other dopants which are notdowndopants may be present in a region of an optical fiber having anegative relative refractive index.

“Chromatic dispersion”, herein referred to as “dispersion” unlessotherwise noted, of a waveguide fiber is the sum of the materialdispersion, the waveguide dispersion, and the inter-modal dispersion. Inthe case of single mode waveguide fibers the inter-modal dispersion iszero. Dispersion slope is the rate of change of dispersion with respectto wavelength.

“Effective area” is defined as:A _(eff)=2π(∫f ² r dr)²/(∫f ⁴ r dr),where the integration limits are 0 to ∞, and f is the transversecomponent of the electric field associated with light propagated in thewaveguide. As used herein, “effective area” or “A_(eff)” refers tooptical effective area at a wavelength of 1550 nm unless otherwisenoted.

The term “α-profile” or “alpha profile” refers to a relative refractiveindex profile, expressed in terms of Δ(r) which is in units of “%”,where r is radius, which follows the equation,Δ(r)=Δ(r _(o))(1−[|r−r _(o)|/(r ₁ −r _(o))]^(α)),where r_(o) is the point at which Δ(r) is maximum, r₁ is the point atwhich Δ(r)% is zero, and r is in the range r_(i)≦r≦r_(f), where Δ isdefined above, r_(i) is the initial point of the α-profile, r_(f) is thefinal point of the α-profile, and α is an exponent which is a realnumber.

The mode field diameter (MFD) is measured using the Peterman II methodwherein, 2w=MFD, and w²=(2∫f² r dr/∫[df/dr]² r dr), the integral limitsbeing 0 to ∞.

The bend resistance of a waveguide fiber can be gauged by inducedattenuation under prescribed test conditions.

One type of bend test is the lateral load microbend test. In thisso-called “lateral load” test, a prescribed length of waveguide fiber isplaced between two flat plates. A #70 wire mesh is attached to one ofthe plates. A known length of waveguide fiber is sandwiched between theplates and a reference attenuation is measured while the plates arepressed together with a force of 30 newtons. A 70 newton force is thenapplied to the plates and the increase in attenuation in dB/m ismeasured. The increase in attenuation is the lateral load attenuation ofthe waveguide.

The “pin array” bend test is used to compare relative resistance ofwaveguide fiber to bending. To perform this test, attenuation loss ismeasured for a waveguide fiber with essentially no induced bending loss.The waveguide fiber is then woven about the pin array and attenuationagain measured. The loss induced by bending is the difference betweenthe two measured attenuations. The pin array is a set of ten cylindricalpins arranged in a single row and held in a fixed vertical position on aflat surface. The pin spacing is 5 mm, center to center. The pindiameter is 0.67 mm. During testing, sufficient tension is applied tomake the waveguide fiber conform to a portion of the pin surface.

The theoretical fiber cutoff wavelength, or “theoretical fiber cutoff”,or “theoretical cutoff”, for a given mode, is the wavelength above whichguided light cannot propagate in that mode. A mathematical definitioncan be found in Single Mode Fiber Optics, Jeunhomme, pp. 39-44, MarcelDekker, New York, 1990 wherein the theoretical fiber cutoff is describedas the wavelength at which the mode propagation constant becomes equalto the plane wave propagation constant in the outer cladding. Thistheoretical wavelength is appropriate for an infinitely long, perfectlystraight fiber that has no diameter variations.

The actual fiber cutoff can be measured by the standard 2m fiber cutofftest, FOTP-80 (EIA-TIA-455-80), to yield the “fiber cutoff wavelength”,also known as the “2m fiber cutoff” or “measured cutoff”. The FOTP-80standard test is performed to either strip out the higher order modesusing a controlled amount of bending, or to normalize the spectralresponse of the fiber to that of a multimode fiber.

The cabled cutoff wavelength, or “cabled cutoff” is even lower than themeasured fiber cutoff due to higher levels of bending and mechanicalpressure in the cable environment. The actual cabled condition can beapproximated by the cabled cutoff test described in the EIA-445 FiberOptic Test Procedures, which are part of the EIA-TIA Fiber OpticsStandards, that is, the Electronics Industry Alliance-TelecommunicationsIndustry Association Fiber Optics Standards, more commonly known asFOTP's. Cabled cutoff measurement is described in EIA-455-170 CableCutoff Wavelength of Single-mode Fiber by Transmitted Power, or“FOTP-170”. By cable cutoff as used herein, we mean the value obtainedusing the approximated test.

Unless otherwise noted herein, optical properties (such as dispersion,dispersion slope, etc.) are reported for the LP01 mode. Unless otherwisenoted herein, a wavelength of 1550 nm is the reference wavelength.

An optical transmission line as used herein includes a length of opticalfiber, or a plurality of optical fibers fused together serially,extending between optical devices, for example between two opticalamplifiers, or between a multiplexing device and an optical amplifier.The optical transmission line may comprise transmission fiber anddispersion compensating fiber, wherein the dispersion compensating fibermay be deployed in a module (DC module) or laid out lengthwise, or both,as selected to achieve a desired system performance or parameter such asresidual dispersion at the end of an optical transmission line.

The optical fiber 10 disclosed herein comprises a core 100 and acladding layer (or cladding) 200 surrounding and directly adjacent thecore. The cladding 200 has a refractive index profile, Δ_(CLAD)(r). Insome embodiments, the cladding 200 consists of pure silica.

Various wavelength bands, or operating wavelength ranges, or wavelengthwindows, can be defined as follows: “1310 nm band” is 1260 to 1360 nm;“E-band” is 1360 to 1460 nm; “S-band” is 1460 to 1530 nm; “C-band” is1530 to 1565 nm; “L-band” is 1565 to 1625 nm; and “U-band” is 1625 to1675 nm.

In some embodiments, the core comprises silica doped with germanium,i.e. germania doped silica. Dopants other than germanium, singly or incombination, may be employed within the core, and particularly at ornear the centerline, of the optical fiber disclosed herein to obtain thedesired refractive index and density.

In some embodiments, the refractive index profile of the optical fiberdisclosed herein is non-negative from the centerline to the inner radiusof the annular segment, R₂. In some embodiments, the optical fibercontains no index-decreasing dopants in the core.

Referring to FIG. 1, optical waveguide fibers 100 are disclosed hereinwhich comprise: a core 20 extending radially outwardly from thecenterline to a central segment outer radius, R₁, and having a relativerefractive index profile, Δ₁(r) in %, with a maximum relative refractiveindex percent, Δ_(1MAX); and, a cladding 200 surrounding and directlyadjacent, i.e. in direct contact with, the core 20. Cladding 200comprises: an annular inner region 30 surrounding the core 20 anddirectly adjacent thereto, extending radially outwardly to an annularinner region outer radius, R₂, having a width W₂ disposed at a midpointR_(2MID), the region 30 having a relative refractive index profile,Δ₂(r) in %, with a maximum relative refractive index percent, Δ_(2MAX),in %, a minimum relative refractive index percent, Δ_(2MIN), in %, and amaximum absolute magnitude relative refractive index percent,|Δ₂(r)|_(MAX); an annular ring region 50 surrounding region 30 anddirectly adjacent thereto, and extending radially outwardly from R₂ toan annular ring region radius, R₃, the region 50 having a width W₃disposed at a midpoint R_(3MID), and having a relative refractive indexprofile, Δ₃(r) in %, with a minimum relative refractive index percent,Δ_(3MIN), in %, wherein Δ_(1MAX)>0>Δ_(3MIN); and an annular outer region60 surrounding the region 50 and directly adjacent thereto and having arelative refractive index percent, Δ_(CLAD)(r) in %. R₁ is defined tooccur at the radius where Δ₁(r) first reaches +0.05%. That is, core 20ends and the annular ring region 30 starts where the relative refractiveindex first reaches +0.05% (going outward radially) at a radius R1, andregion 30 is defined to end at a radius R2 where the relative refractiveindex Δ₂(r) first reaches −0.05% (going outward radially). The annularring region 50 begins at R₂ and ends at R₃ for this group ofembodiments. R₃ is defined to occur where the relative refractive indexΔ₃(r) first reaches −0.05% (going outward radially) after Δ₃(r) hasdipped to at least −0.1%. The width W₃ of the annular segment is R₃−R₂and its midpoint R_(3MID) is (R₂+R₃)/2. In some embodiments, more than90% of the radial width of the central segment has a positive relativerefractive index, and in some embodiments Δ₁(r) is positive for allradii from 0 to R₁. In some embodiments, |Δ₂(r)|<0.025% for more than50% of the radial width of the annular inner region 30, and in otherembodiments |Δ₂(r)|<0.01% for more than 50% of the radial width of theannular inner region 30. Δ₃(r) is negative for all radii from R₂ to R₃.Preferably, Δ_(CLAD)(r)=0% for all radii greater than 30 μm. The coreends and the cladding begins at a radius R_(CORE). Cladding 200 extendsto a radius, R₄, which is also the outermost periphery of the glass partof the optical fiber. Also, Δ_(1MAX)>Δ_(2MAX)>Δ_(3MIN), andΔ_(MAX)>Δ_(2MIN)>Δ_(3MIN).

The core has a profile volume, V₁, defined herein as:

2∫₀^(R₁)Δ₁(r)𝕕r.

The annular ring region has a profile volume, V₃, defined herein as:

2∫_(R₂)^(R₃)Δ₃(r)𝕕r.

Preferably, Δ_(1MAX)<0.45%, Δ_(2MIN)>−0.05%, Δ_(2MAX)<0.05%,Δ_(3MIN)<−0.63%, 0.2<R₁/R₂<0.6, and the absolute magnitude of theprofile volume of the annular ring region, |V₃|, is greater than20%-μm². More preferably, Δ_(3MIN)<−0.65%, and even more preferably≦−0.7%. In some embodiments, 0.35<R₁/R₂<0.5. When we say, for example,Δ<−0.63%, we mean Δ is more negative than −0.63%.

Preferably, W₂>⅔ R₁, and in some embodiments W₂>2 μm.

In some embodiments, 20%-μm²<|V₃|<80%-μm². In other embodiments,30%-μm²<|V₃|<70%-μm². In other embodiments, 40%-μm²<|V₃|<60%-μm².

Preferably, 0.28%<Δ_(1MAX)<0.45%, more preferably 0.30%<Δ_(1MAX)<0.40%,and in some embodiments 0.31%<Δ_(1MAX)<0.38%.

Preferably, R₁<5.0 μm, more preferably 3.0 μm<R₁<5.0 μm, and in someembodiments 4.0 μm<R₁<5.0 μm.

Preferably, R₂>8.0 μm, and in some embodiments 8.0 μm<R₂<15.0 μm.

Preferably, R₃>10.0 μm, and in some embodiments 10.0 μm<R₃<20.0 μm.

In some embodiments W₃>1.0 μm, and in other embodiments 1.0<W₃<6.0 μm,and in other embodiments 1.0<W₃<5.0 μm.

Preferably, R₄>40 μm. In some embodiments, R₄>50 μm. In otherembodiments, R₄>60 μm. In some embodiments, 60 μm<R₄<70 μm.

In some embodiments, the central segment of the core may comprise arelative refractive index profile having a so-called centerline dipwhich may occur as a result of one or more optical fiber manufacturingtechniques. For example, the central segment may have a local minimum inthe refractive index profile at radii less than 1 μm, wherein highervalues for the relative refractive index (including the maximum relativerefractive index for the, core segment) occur at radii greater than r=0μm.

Preferably, the optical fiber disclosed herein provides: a mode fielddiameter at 1310 nm of 8.20 μm to 9.50 μm, more preferably 8.4 μm to9.20 μm; a zero dispersion wavelength between 1300 and 1324 nm; and acable cutoff wavelength less than 1260 nm. As the cable cutoffwavelength is not more than (and in some embodiments about equal to) the2m fiber cutoff wavelength, a 2m fiber cutoff wavelength of less than1260 nm results in a cable cutoff wavelength less than 1260 nm.

1^(st) Set of Embodiments

Tables 1-2 list characteristics of illustrative examples, Examples 1-7,of a first set of embodiments. The refractive index profiles of Examples2-7 are similar to FIG. 1 with the following respective values.

TABLE 1 Example 1 2 3 4 5 6 7 Δ_(1MAX) % 0.38 0.35 0.38 0.38 0.38 0.380.34 R₁ μm 4.4 4.5 4.4 4.4 4.4 4.4 4.6 α₁ 10 10 10 10 10 10 10 V₁ %-μm²5.95 5.76 5.95 5.95 5.95 5.95 5.96 R₂ μm 10.3 10.4 9.7 11.6 9.5 12.712.1 R₁/R₂ 0.43 0.43 0.45 0.38 0.46 0.35 0.38 W₂ μm 5.9 5.9 5.3 7.2 5.18.3 7.5 R_(2MID) μm 7.4 7.5 7.1 8.0 7.0 8.6 8.4 Δ_(3MIN) % −0.80 −0.79−0.77 −0.75 −0.72 −0.72 −0.72 R₃ = R_(CORE) μm 14.0 13.3 12.7 13.8 12.115.0 13.9 W₃ μm 3.7 2.9 3.0 2.2 2.6 2.3 1.8 R_(3MID) μm 12.2 11.9 11.212.7 10.8 13.9 13.0 |V₃| %-μm² 62.8 44.7 44.0 34.0 32.2 36.3 26.1

TABLE 2 Example 1 2 3 4 5 6 7 Dispersion ps/nm-km 0.24 0.45 0.49 −0.140.53 −0.30 0.30 @1310 nm Slope ps/nm²-km 0.089 0.090 0.090 0.088 0.0900.087 0.088 @1310 nm Lambda Zero nm 1307 1305 1305 1312 1304 1313 1307MFD μm 8.68 8.98 8.66 8.71 8.65 8.72 9.21 @1310 nm MFD μm 9.74 10.089.68 9.84 9.67 9.88 10.40 @1550 nm Aeff μm² 72.9 78.0 72.2 74.0 72.174.5 82.8 @1550 nm Pin Array dB 3 8 4 4 4 4 9 @1550 nm Lateral Load dB/m0.14 0.32 0.16 0.19 0.18 0.20 0.46 @1550 nm LP11 theoretical nm 12411220 1235 1252 1233 1259 1253 LP02 theoretical nm 779 767 776 784 776787 784 Fiber Cutoff nm 1232 1208 1223 1228 1211 1232 1216 (2 meter)Attenuation dB/km 0.340 0.338 0.340 0.340 0.340 0.340 0.338 @1310 nmAttenuation dB/km 0.278 0.277 0.278 0.278 0.278 0.279 0.277 @1380 nmAttenuation dB/km 0.193 0.191 0.192 0.193 0.193 0.193 0.191 @1550 nmDispersion ps/nm-km 18.1 18.4 18.5 17.2 18.4 16.7 17.7 @1550 nm Slopeps/nm²-km 0.064 0.064 0.064 0.062 0.064 0.061 0.062 @1550 nm

In some embodiments, such as Examples 1-7, the optical fiber exhibitsmode field diameter at 1310 nm of 8.60 μm to 9.30 μm; a zero dispersionwavelength between 1300 and 1324 nm; and 2m fiber cutoff wavelength ofless than 1260 nm, which results in a cable cutoff wavelength less than1260 nm. Additionally, the 2m fiber cutoff wavelength is preferably nottoo low, thereby preventing bend losses from being too high. Forexample, the 2m fiber cutoff wavelengths of the embodiments of Examples1-7 are greater than 1190 nm and less than 1260 nm.

The optical fibers disclosed herein exhibit superior bend resistance,both macrobend and microbend. The pin array bend loss at 1550 nm(attenuation increase associated with the optical fiber tested in a pinarray), one measure of macrobend loss, is less than 15 dB, preferablyless than 10 dB, and in some embodiments less than 5 dB. Also, thelateral load wire mesh loss at 1550 nm, one measure of microbend loss,is less than 0.5 dB, preferably less than 0.3 dB, and in someembodiments less than 0.2 dB.

We have also found that the LP11 theoretical cutoff wavelength generallycan serve as an upper bound on the 2m fiber cutoff wavelength for theoptical fiber disclosed herein. As illustrated by Examples 1-7, the LP11theoretical cutoff wavelength is less than 1270 nm, preferably less than1265 nm, and even more preferably less than 1260 nm. We have also foundthat for a given core profile, increasing the magnitude of the profilevolume, |V₃|, without limit causes the cutoff wavelength to increase tothe point that the optical fiber is multimoded at 1310 nm or even at1550 nm. Accordingly, in some embodiments, 20%-μm²<|V₃|<80%-μm², inother embodiments 30%-μm²<|V₃|<70%-μm², and in other embodiments40%-μm²<|V₃|<60%-μm².

We have also found that a higher core volume generally not only tends toincrease the size of the mode field, but also raises the LP11theoretical cutoff wavelength, and therefore tends to raise the 2m fibercutoff wavelength. In some embodiments, the profile volume of the core,V1, is greater than 0 and less than 6.5%-μm², in other embodiments lessthan 6.2%μm², and in some embodiments, such as Examples 1-7, V₁ isbetween 5.50 and 6.00%-μm².

The core 20 shown in FIG. 1 has a refractive index profile with an alphashape, wherein α₁ is about 10. However, the core 20 could have othervalues of α₁, or the core could have a profile shape other than an alphaprofile, such as a multi-segmented core.

EXAMPLE 8

An optical fiber was manufactured via outside vapor deposition. Themeasured relative refractive index profile of the optical fiber is shownin FIG. 2. A germania doped silica glass core cane with a pure silicacladding served as a bait rod for chemical vapor deposition of a glasssoot layer which was doped with fluorine and consolidated, then an outerlayer of glass soot was applied and consolidated, to form an opticalfiber preform. The preform was drawn into optical fiber having agermania doped core 20 surrounded by and in contact with a cladding 200,the cladding 200 having an annular inner region 30, an annular ringregion 50, and an annular outer region 60, wherein Δ_(1MAX)=0.43%,R₁=4.6 μm, R₂=8.5 μm, Δ_(3MIN)=−0.70%, R₃=11.7 μm, W₂=3.9, W₃=3.2,R₁/R₂=0.54, V₁=6.4, and V₃=−28.3 (|V₃|=28.3). The measured 20 mmdiameter bend test results (wrapping the optical fiber around a 20 mmdiameter mandrel) at 1550 nm were: 0.028 dB/turn for 1 turn around the20 mm dia. mandrel, and 0.126 dB/turn for 5 turns around the mandrel.The measured 10 mm diameter bend test results (wrapping the opticalfiber around a 10 mm diameter mandrel) at 1550 nm was: 0.60 dB/turn for1 turn around the 10 mm dia. mandrel. The measured MFD was 8.27 μm and9.24 μm at 1310 nm and 1550 nm, respectively. The 2m fiber cutoff was1251 nm.

FIG. 3 is a schematic representation (not to scale) of an opticalwaveguide fiber 100 as disclosed herein having core 20 and a cladding200 directly adjacent and surrounding the core 20, the cladding 200being comprised of an annular inner region 30, an annular ring region50, and an annular outer region 60. The core 20 can have one or aplurality of core segments.

The clad layer 200 may be comprised of a cladding material which wasdeposited, for example during a laydown process, or which was providedin the form of a jacketing, such as a tube in a rod-in-tube opticalpreform arrangement, or a combination of deposited material and ajacket. The clad layer 200 is surrounded by at least one coating 210,which may in some embodiments comprise a low modulus primary coating anda high modulus secondary coating.

Preferably, the optical fiber disclosed herein has a silica-based coreand cladding. In preferred embodiments, the cladding has an outerdiameter, 2*Rmax, of about 125 μm. Preferably, the outer diameter of thecladding has a constant diameter along the length of the optical fiber.In preferred embodiments, the refractive index of the optical fiber hasradial symmetry. Preferably, the outer diameter of the core has aconstant diameter along the length of the optical fiber. Preferably, oneor more coatings surround and are in contact with the cladding. Thecoating is preferably a polymer coating such as acrylate. Preferably thecoating has a constant diameter, radially and along the length of thefiber.

As shown in FIG. 4, an optical fiber 100 as disclosed herein may beimplemented in an optical fiber communication system 330. System 330includes a transmitter 334 and a receiver 336, wherein optical fiber 100allows transmission of an optical signal between transmitter 334 andreceiver 336. System 330 is preferably capable of 2-way communication,and transmitter 334 and receiver 336 are shown for illustration only.The system 330 preferably includes a link which has a section or a spanof optical fiber as disclosed herein. The system 330 may also includeone or more optical devices optically connected to one or more sectionsor spans of optical fiber as disclosed herein, such as one or moreregenerators, amplifiers, or dispersion compensating modules. In atleast one preferred embodiment, an optical fiber communication systemaccording to the present invention comprises a transmitter and receiverconnected by an optical fiber without the presence of a regeneratortherebetween. In another preferred embodiment, an optical fibercommunication system according to the present invention comprises atransmitter and receiver connected by an optical fiber without thepresence of an amplifier therebetween. In yet another preferredembodiment, an optical fiber communication system according to thepresent invention comprises a transmitter and receiver connected by anoptical fiber having neither an amplifier nor a regenerator nor arepeater therebetween.

Preferably, the optical fibers disclosed herein have low water content,and preferably are low water peak optical fibers, i.e. having anattenuation curve which exhibits a relatively low, or no, water peak ina particular wavelength region, especially in the E-band.

Methods of producing low water peak optical fiber can be found in U.S.Pat. No. 6,477,305, U.S. Pat. No. 6,904,772, and PCT ApplicationPublication No. WO01/47822.

All of the optical fibers disclosed herein can be employed in an opticalsignal transmission system, which preferably comprises a transmitter, areceiver, and an optical transmission line. The optical transmissionline is optically coupled to the transmitter and receiver. The opticaltransmission line preferably comprises at least one optical fiber span,which preferably comprises at least one section of the optical fiberdisclosed herein. The optical transmission line may also comprise asection of a second optical fiber having a negative dispersion at awavelength of about 1550 nm, for example to effect dispersioncompensation within the optical transmission line.

FIG. 5 schematically illustrates another embodiment of an optical fibercommunication system 400 disclosed herein. System 400 includes atransmitter 434 and a receiver 436 which are optically connected byoptical transmission line 440. Optical transmission line 440 comprises afirst fiber 442 which is a low attenuation large effective area opticalfiber as disclosed herein, and a second optical fiber 444 having anegative dispersion at 1550 nm. The first fiber 442 and second fiber 444may be optically connected by a fusion splice, an optical connector orthe like, as depicted by the symbol “X” in FIG. 5. The opticaltransmission line 440 may also comprise one or more components and/orother optical fiber(s) (for example one or more “pigtail fibers” 445 atjunctions between fibers and/or components). In preferred embodiments,at least a portion of the second optical fiber 444 is optionallydisposed within a dispersion compensating module 446. Opticaltransmission line 440 allows transmission of an optical signal betweentransmitter 434 and receiver 436. The system preferably furthercomprises at least one amplifier, such as a Raman amplifier, opticallycoupled to the optical fiber section. The system further preferablycomprises a multiplexer for interconnecting a plurality of channelscapable of carrying optical signals onto the optical transmission line,wherein at least one, more preferably at least three, and mostpreferably at least ten optical signals propagate at a wavelengthbetween about 1260 nm and 1625 nm. Preferably, at least one signalpropagates in one or more of the following wavelength regions: the 1310nm band, the E-band, the S-band, the C-band, and the L-band.

In some preferred embodiments, the system is capable of operating in acoarse wavelength division multiplex mode wherein one or more signalspropagate in at least one, more preferably at least two of the followingwavelength regions: the 1310 nm band, the E-band, the S-band, theC-band, and the L-band. In one preferred embodiment, the system operatesat one or more wavelengths between 1530 and 1565 nm.

It is to be understood that the foregoing description is exemplary ofthe invention only and is intended to provide an overview for theunderstanding of the nature and character of the invention as it isdefined by the claims. The accompanying drawings are included to providea further understanding of the invention and are incorporated andconstitute part of this specification. The drawings illustrate variousfeatures and embodiments of the invention which, together with theirdescription, serve to explain the principals and operation of theinvention. It will become apparent to those skilled in the art thatvarious modifications to the preferred embodiment of the invention asdescribed herein can be made without departing from the spirit or scopeof the invention as defined by the appended claims.

1. An optical fiber comprising: a glass core extending from a centerlineto a radius R₁; a glass cladding surrounding and in contact with thecore, the cladding comprising: an annular inner region extending from R₁to a radius R₂, the inner region comprising a radial width, W₂=R₂−R₁, anannular ring region extending from R₂ to a radius R₃, the ring regioncomprising a radial width, W₃=R₃−R₂, and an annular outer regionextending from R₃ to an outermost glass radius R₄; wherein the corecomprises a maximum relative refractive index, Δ_(1MAX), relative to theouter region, and Δ_(1MAX)<0.45%; wherein the annular inner regioncomprises a radial width, W₂, a minimum relative refractive index,Δ_(2MIN), relative to the outer region, and a maximum relativerefractive index, Δ_(2MAX), relative to the outer region, whereinΔ_(2MIN)>−0.05%, Δ_(2MAX)<0.05%, and W₂>⅔ R₁; wherein the annular ringregion comprises: a minimum relative refractive index, Δ_(3MIN),relative to the annular outer region, wherein Δ_(3MIN)<−0.63%; whereinΔ_(1MAX)>Δ_(2MAX)>Δ_(3MIN), and Δ_(MAX)>Δ_(2MIN)>Δ_(3MIN); and whereinthe core and the cladding provide a cable cutoff less than 1260 nm, azero dispersion between 1300 and 1324 nm, a mode field diameter at 1310nm of between 8.20 and 9.50 μm, and a 10 mm diameter mandrel bend lossof less than 1.0 dB/turn.
 2. The optical fiber of claim 1 wherein thecore and the cladding provide a 20 mm diameter mandrel bend loss of lessthan 0.05 dB/turn.
 3. The optical fiber of claim 1 wherein the core andthe cladding provide a pin array bend loss at 1550 nm of less than 10dB.
 4. The optical fiber of claim 1 wherein the annular ring regioncomprises a profile volume, V₃, equal to: 2∫_(R₂)^(R₃)Δ(r)𝕕r; wherein|V₃|>20%-μm².
 5. The optical fiber of claim 1 wherein 0.2<R1/R2<0.6. 6.An optical fiber comprising: a glass core extending from a centerline toa radius R₁; a glass cladding surrounding and in contact with the core,the cladding comprising: an annular inner region extending from R₁ to aradius R₂, the inner region comprising a radial width, W₂=R₂−R₁, anannular ring region extending from R₂ to a radius R₃, the ring regioncomprising a radial width, W₃=R₃−R₂, and an annular outer regionextending from R₃ to an outermost glass radius R₄; wherein the corecomprises a maximum relative refractive index, Δ_(1MAX), relative to theouter region, and Δ_(1MAX)<0.45%; wherein the annular inner regioncomprises a radial width, W₂, a minimum relative refractive index,Δ_(2MIN), relative to the outer region, and a maximum relativerefractive index, Δ_(2MAX), relative to the outer region, whereinΔ_(2MIN)>−0.05%, Δ_(2MAX)<0.05%, and W₂>⅔ R₁; wherein the annular ringregion comprises: a minimum relative refractive index, Δ_(3MIN),relative to the annular outer region, wherein Δ_(3MIN)<−0.63%, and aprofile volume, V₃, equal to: 2∫_(R₂)^(R₃)Δ(r)𝕕r; wherein |V₃|>20%-μm²;wherein Δ_(1MAX)>Δ_(2MAX)>Δ_(3MIN), and Δ_(MAX)>Δ_(2MIN)>Δ_(3MIN); andwherein 0.2<R₁/R₂<0.6.
 7. The optical fiber of claim 6 wherein0.4<R₁/R₂<0.6.
 8. The optical fiber of claim 6 wherein20%-μm²<|V₃|<80%-μm².
 9. The optical fiber of claim 6 wherein0.28%<Δ_(1MAX)<0.45%.
 10. The optical fiber of claim 6 wherein R₁<5.0μm.
 11. The optical fiber of claim 6 wherein R₂>8 μm.
 12. The opticalfiber of claim 6 wherein R₃>10 μm.
 13. The optical fiber of claim 6wherein W₃ is between 2 and 5 μm.
 14. The optical fiber of claim 1wherein the core comprises a profile volume, V₁, equal to:2∫₀^(R₁)Δ(r)𝕕r; wherein V₁ is greater than 0 and less than 6.2%-μm². 15.The optical fiber of claim 6 wherein the core and the cladding provide acable cutoff less than 1260 nm.
 16. The optical fiber of claim 6 whereinthe core and the cladding provide a zero dispersion between 1300 and1324 nm.
 17. The optical fiber of claim 6 wherein the core and thecladding provide a mode field diameter at 1310 nm of between 8.20 and9.50 μm.
 18. The optical fiber of claim 6 wherein the core and thecladding provide a 10 mm diameter mandrel bend loss of less than 1.0dB/turn.
 19. The optical fiber of claim 6 wherein the core and thecladding provide a 20 mm diameter mandrel bend loss of less than 0.05dB/turn.
 20. The optical fiber of claim 6 wherein the core and thecladding provide a pin array bend loss at 1550 nm of less than 10 dB.21. The optical fiber of claim 1 wherein the annular ring regioncomprises fluorine.
 22. The optical fiber of claim 1 wherein said fibercomprises a fiber cutoff less than 1260 nm.